Still a chance of big quake | Canterbury News | Local News in Canterbury

The energy release from the thousands of aftershocks is not taking the pressure off another big quake happening.

Victoria University professor Martha Savage revealed yesterday it was a myth that small aftershocks were preventing bigger earthquakes by relieving stress on fault lines.

"It's not correct. That's what the people of L'Aquila (Italy) thought and they stayed in their homes. I don't want to scare people but small aftershocks do increase the risk of bigger quakes by a small amount. All aftershocks can increase stress."

Her statements come at the same time a new study conducted by Italian seismologists has suggested that last September's 7.1 quake in Darfield had a role in causing February 22's deadly quake.

The Italians analysed ground data from a Japanese satellite and found the Darfield quake may have loaded stress onto the Port Hills fault, contributing to its rupture in February.

Although the study, published in the nature journal Scientific Reports, could not determine whether or not the February earthquake was likely to occur without the September quake, they did conclude that the first quake brought the Port Hills fault closer to failure.

The researchers were working off the Coulomb Stress Triggering Theory, an approach which assumes that after an earthquake the stress spreads to the surrounding area - potentially increasing the occurrence of further earthquakes.

They were unable to determine whether the Christchurch quake was an aftershock of the Darfield quake or a seismic event in its own right.

The research comes at the same time as six seismologists are on trial in Italy for manslaughter, after failing to predict the 2009 earthquake which killed 309 people in L'Aquila.

The prosecutors say the seismologists gave a falsely reassuring statement the week before the deadly quake occurred, after studying hundreds of tremors that had shaken the city.